The perfect way to say congratulations for staying married would be to give the happy couple some swimwear. It would allow them to bond and get closer by participating in a beaching event that brings pleasure and enjoyment. You could get matching outfits geared for a man and woman. Get a sexy yellow and blue string bikini for her with matching yellow and blue trunks for him. Throw in some accessories that will allow them to dress up to express their individual selves plus mesh together as a married couple. Sunglasses, hats, sandals and jewelry are added options which would make the experience very culpable.
The husband will really appreciate the gift loving to see his wife in something so hot and sexy. She will also delight in seeing her prince charming wearing something nice as well. They can frolick together on the beach wearing the same designed summer wear catching the eyes of envious people from all over.
Show them that you want to keep their relationship alive and vibrant by giving them something they'll both enjoy and bring them closer together.